The present invention relates to a wireless communication system and a wireless communication method and, particularly, to a wireless communication system and a wireless communication method that can introduce a system using RFID (Radio Frequency IDentification) technology into the wireless network environment.
A system using RFID attracts attention and has begun to be applied to various uses. The basic configuration of the system using RFID includes an RFID reader/writer that performs data communication with an RFID radio tag via radio and a computer terminal that controls the RFID reader/writer. The RFID reader/writer can read or write data stored in the radio tag (cf. International Solid-State Circuits Conference 2006, Digest of Technical Papers, Lecture No. 17.2).
The RFID radio tag does not have a battery built in because it generates a power supply voltage using a radio wave when transmitting and receiving data to and from the RFID reader/writer. Such a radio tag is generally called “passive”. Specifically, in the RFID radio tag, a radio wave (part of a carrier wave) supplied from the RFID reader/writer is rectified from alternating current to direct current by a full-wave rectifier. After that, the voltage is stepped up or down to a suitable voltage as a circuit power supply by an internal voltage control circuit or a booster circuit, and then the power is supplied as a power supply to an internal circuit such as a current mode demodulator or a logic circuit. In this case, the efficiency of the conversion from alternating current to direct current in the RFID radio tag can be enhanced by optimizing the device size of a PMOS/NMOS rectifying diode included in the full-wave rectifier or reducing a loss due to parasitic capacitance or the like before input to the rectifying diode and a loss due to mismatch between an antenna and a rectifying input.
Further, a technique related to an indoor intruder detection apparatus is disclosed in Japanese Unexamined Patent Application Publication No. H07-141577. The indoor intruder detection apparatus disclosed therein includes a transmitting device, a receiving device, and an alarm device. The transmitting device transmits a non-modulated wave signal with a given carrier frequency. The receiving device includes a receiving unit that receives a signal output from the transmitting device, a detecting unit that detects the received signal, and a level variation detection unit that outputs a detection signal when the level of the signal obtained by the detecting exceeds a predetermined range. The alarm device raises an alarm based on the detection signal output from the level variation detection unit of the receiving device. The indoor intruder detection apparatus disclosed in Japanese Unexamined Patent Application Publication No. H07-141577 detects indoor intruder based on the variation of the received electric field of a radio wave output from the transmitting device and the variation of the bit error rate of a demodulated signal.